1. Field of the Invention
Embodiments of the invention are directed to methods and related systems of improving image quality when overlaying a digital graphics object on a digital picture. More particularly, the embodiments of the invention are directed to detecting and correcting pixels in the graphic object with slight color-key variation caused by scaling and/or filtering.
2. Description of the Related Art
Digital pictures, whether a single picture or a series of pictures representing video, may be modified by the addition of special effects, such as overlaying a graphics object on the digital picture. The graphics object may contain features such as borders, titles, and/or dates that are inserted into the picture or pictures.
In order to distinguish graphics objects pixels that should replace pixels in the digital picture from graphics object pixels that are not intended to replace pixels in the digital picture, a color-key system may be used. In a color-key system, a particular color is designated as the color-key, and during an overlay process pixels having the value of the color-key are not inserted into the digital picture. Stated oppositely, when a graphics object pixel does not hold the color-key value the graphics object pixel replaces the corresponding pixel within the digital picture.
However, graphics objects intended to be overlaid on digital pictures may not necessarily be the correct size. To make a graphics object larger, a scaling routine may add pixels to the picture, and select colors for the added pixels. Likewise, in making a graphics object smaller a scaling routine may be responsible for removing and/or combining pixels, and selecting appropriate colors for the newly formed pixels. In the process of scaling, the scaling program may inadvertently change the values of color-key pixels within the graphics object. Changes to the color-pixels may also occur when the graphics object is digitally filtered.
Regardless of the mechanism by which a color-key pixel's color is changed, in the overlay process errant pixels are assumed to be part of the graphics object and thus are written to the digital picture, affecting image quality.